It is known to construct structural panels from a composite material comprising layers of a structural fiber (e.g. graphite fibers) within a matrix. The use of such composite material for making an aircraft panel structure is discussed in U.S. Pat. No. 4,463,044, granted July 31, 1984 to Mauricee McKinney.
In use, damage type holes can be formed in the panel material. The standard way of repairing such holes is to form a tapered recess in the composite material around the hole. Disk-shaped layers of structural fiber cloth, of different diameters, are set into the recess. The fibers of each layer are oriented at a different angle to the fibers of the adjoining layer. The layers are secured in place by the use of high strength adhesives. A problem with these adhesives is that they require a long cure time. Also, this method of repair requires a highly trained technician and the repaired area relies totally on the adhesives to transfer the design load across the repair. A similar technique is disclosed by U.S. Pat. No. 4,554,036, granted Nov. 19, 1985, to Cosby M. Newsom. Other repair techniques, known in the patent literature, are disclosed by U.S. Pat. No. 4,517,038, granted May 14, 1985 to Robert W. Miller, and U.S. Pat. No. 4,560,428, granted Dec. 24, 1985 to George O. Sherrick and Joseph R. Rosenthal.